Your best bet is childrens tylenol (no more than 1/4 ml every 4 hours) and humidifier. Cold medicine that you find OTC is not safe for young children and you will see more side effects if the child takes OTC cold medicine. I wish you the best and hope your little one feels better.
They don't make cold medication for infants anymore after they pulled it all off the market three or four years ago. The children's stuff, I'd imagine is too concentrated, and too strong for a baby. Like someone else said, infant Tylenol is probably about the only thing you can give him, and I'd definitely put the humidifier in with him. When my daughter was congested at that age, I'd strap her into her bouncy seat to sleep (because then she was in a reclining position instead of flat on her back) and I'd sleep on a mattress on the floor with my head next to her bouncy seat in case she started trying to roll out of the restraints. (It made it easier too, to just gently bounce her back to sleep then when she woke up.)
I had this issue with my son when he was about 4 months. My pediatrician said not to give him anything. Just use a humidifier (told me to not even use infant Vicks because it can cause burns on their skin.) He said only to give Tylenol if he started running a fever. Besides that he said to use Infant saline nasal drops and a bulb sucker. Good luck and hope this helps.